Uniform ZIF-67@17-FAS/PVDF superhydrophobic nanofibrous membrane via co-solvent strategy for membrane distillation

Co-solvent method to precisely reduce the polarity for preparing uniform ZIF-67 nanoparticles. • 17-FAS promotes interfacial compatibility between ZIF-67 and PVDF and increases wetting resistance. • High water flux of 24.7 kg·m −2 ·h −1 with only 3.01% decline rate after 72 h DCMD. Membrane distillation (MD) offers distinct advantages for wastewater treatment, including low operational demands and near-perfect solute rejection. However, its long-term application is severely hindered by issues such as material detachment, membrane deformation, and wetting. Here, a co-solvent-assisted synthesis strategy with n-heptane and methanol was proposed to prepare uniform ZIF-67 nanoparticles. By optimizing the fiber diameter, robust integration of ZIF-67 with the PVDF matrix is achieved. Furthermore, the incorporation of 1 H,1 H,2 H,2H-perfluorodecyltriethoxysilane (17-FAS) significantly improves interfacial adhesion between ZIF-67 and PVDF, effectively preventing particle detachment and reinforcing wetting resistance during prolonged operation. The successful incorporation of ZIF-67 and 17-FAS was confirmed by FTIR and XPS analyses, and SEM and AFM observations revealed the micro-rough morphology of membrane surface. The enhanced mechanical properties and thermal stability of the composite membranes were verified by tensile testing and TGA. The developed ZIF-67@17-FAS/PVDF membrane exhibits a high water contact angle of 156.6° and the permeate flux of 24.7 kg·m −2 ·h −1 with 3.01% decline rate for 3.5 wt% NaCl solution within 72 h of direct contact membrane distillation (DCMD). Remarkably, under a high-salinity condition of 10 wt%, the flux decline rate is only 7.01%, demonstrating outstanding long-term stability. This work provides a promising strategy to overcome the key limitations of MD membranes through synergistic size control, structural optimization, and interfacial engineering. Download: Download high-res image (178KB) Download: Download full-size image